Composite brazing materials composed of individual layers of aluminum alloy sheets, each sheet being made of a different alloy, have been known for some time. A typical brazing material which has found use in the automotive industry is described in U.S. Pat. Nos. 3,853,547 and 3,898,053 to O. R. Singleton, Jr. These patents describe a composite material formed of an alloy core made of 3000 series or 5000 series aluminum alloy core material clad on one or both sides with a 4104 aluminum alloy cladding sheet. Specific core materials mentioned are 3003, 3004, 3105, 5005, 5052 and 5457 alloys.
Bonds in the composite material directly between the high manganese content 3000 alloy series core and the high silicon content 4104 alloy cladding sheet are difficult to make, however. The failure of the materials to bond consistently during hot rolling formation, or the subsequently delamination of a poorly formed bond, causes significant waste of product and equipment time for the manufacturer. Consequently, it would be advantageous to have means which would provide for improved bonding in a composite brazing material between a high silicon content aluminum alloy cladding sheet and a high manganese content aluminum alloy core sheet.